This invention relates to systems and methods for providing constant loading in AC power applications.
It is well known that electric motors waste power when not operating at maximum load. In order to improve the efficiency of such motors and other electronic devices, energy savings devices are commonly employed. Currently, energy savings devices utilize various devices in which to alter an incoming modulating sine wave of an alternating current, which is also known as an AC current. In order to realize an energy savings, direct pulse width modulation (PWM) (or modulation of a pulse carrier wherein the value of each instantaneous sample of a modulating wave produces a pulse of proportional duration by varying the leading, trailing, or both edges of a pulse and which is also known as pulse-duration modulation) is employed by most energy savings devices. These devices “phase-chop” the incoming modulating sine wave, meaning that at least one portion of an area under the curve of the incoming modulating sine wave is removed. Thus, at varying instances during the modulating sine wave, the alternating current increases to a maximum height and then suddenly drops to zero per half cycle. In essence, the alternating current is being turned on and turned off at various times during each half cycle.
Although phase-chopping does, in fact, reduce energy, the interruption in power by removing the portions cause, among other things, increased harmonic content and un-even loading on a generator and power transmission system. Due to these effects, optimum utilization of incoming AC power is not achieved.
Furthermore, most electrical devices rely on a constant loading of AC power and are manufactured as such. Thus, the electrical devices are programmed to depend on receipt of constant loading of AC power. Any deviation in timing or frequency of the AC power could affect the overall performance of the electrical device.
When AC power is chopped using a triode alternating current switch (TRIAC), a silicone controlled rectifier (SCR), a field effect transistor (FET) or an insulated gate bipolar transistor (IGBT) devices, the latter part of each half cycle of the incoming modulating sine wave is repeatedly used. Under such circumstances, although the overall energy load is reduced, the load across each half cycle is repetitively unbalanced. The repetitive unbalance of load on each half cycle ultimately results in compromised performance of the electrical devices in which the energy savings device is connected thereto.
Thus, a need exists for a system and method for providing constant loading in AC power applications.
The relevant patents of prior art includes the following references:
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